GQ honours NFL quarterback who sparked debate over race-based police brutality by kneeling during US national anthem.

Colin Kaepernick, an American football player who last year started protesting police brutality against African Americans by kneeling during the US national anthem, has been named "Citizen of the Year" by GQ magazine.

The public stand of the former San Francisco 49ers quarterback, who is currently without a team, has sparked a wave of similar protests across the National Football League and other athletic events.

Announcing its decision on Monday, GQ likened Kaepernick to American sports icons, including boxer Muhammad Ali, who opposed the Vietnam War.

"He's been vilified by millions and locked out of the NFL - all because he took a knee to protest police brutality," the magazine said of Kaepernick's protest.

"It cost him his job. It also transformed Colin Kaepernick into a lightning rod and a powerful symbol of activism and resistance.

"Kaepernick's determined stand puts him in rare company in sports history: Muhammad Ali, Jackie Robinson - athletes who risked everything to make a difference," it said.

Kaepernick declined to be interviewed by GQ but posed for pictures. He posted a message on Twitter, saying he was "honoured' by the recognition.

Kaepernick's protest against police brutality that disproportionately targets African Americans started in August 2016, but it quickly spread throughout the league and has continued to inspire athletes to kneel during the national anthem well into the 2017 season.